Base your answers to questions 75 and 76 on the
information below and on your knowledge of chemistry.
During the winter months, icy roads pose a threat to
motorists and can lead to accidents. A mixture of sand and sodium
chloride, NaCl, can be spread on roads to make winter driving safer. One
New York town requires that a mixture of sand and salt used on
residential roads should contain 25% or less of NaCl by mass. A
10.0-gram sample of a mixture of sand and NaCl was analyzed and found to
contain 3.3 grams of NaCl.
75 State, in terms of freezing point, why sodium
chloride is part of the mixture put on icy roads. 
Answer--> A NaCl solution has a lower
freezing point than water.
76 Explain, in terms of composition by mass, why the
mixture from which the analyzed sample was taken should not be used
on residential roads of the town. 
Answer--> The sample is greater than
25% NaCl by mass.